Blood is a vital fluid in the human body, composed of several key components. The main parts include red blood cells, which transport oxygen; white blood cells, which help fight infections; and platelets, which assist in blood clotting. These components are suspended in a liquid called plasma, which makes up about 55% of blood volume and contains water, nutrients, hormones, and waste products. The composition of blood is crucial for maintaining overall health. Red blood cells contain hemoglobin, a protein that binds oxygen, while white blood cells are essential for the immune response. Platelets play a critical role in healing wounds, and plasma serves as a medium for transporting various substances throughout the body.